MPX4115A gives random values. Faulty sensor or what?

Other Hardware Sensors
1 
int pressureValue;
float pressure;
void setup ( ) {
  Serial.begin (9600);
}
void loop ( ) {
  pressureValue = analogRead (A1);
  pressure = ((pressureValue / 1024.0) + 0.095) / 0.0009;
  Serial.print("Pressure = ");
  Serial.print(pressure);
  Serial.println (" millibars");
  delay (2000);
}

Sensor gives values like these:

Pressure = 363.80 millibars
Pressure = 467.97 millibars
Pressure = 509.20 millibars
Pressure = 394.18 millibars
Pressure = 331.25 millibars
Pressure = 431.08 millibars
Pressure = 525.48 millibars
Pressure = 466.88 millibars
Pressure = 356.21 millibars
Pressure = 368.14 millibars
Pressure = 489.67 millibars
Pressure = 504.86 millibars
Pressure = 393.10 millibars
Pressure = 341.02 millibars

First of all, result are too low and they seems to be random. Is sensor faulty?

2

Is the sensor in fact connected to A1?

If so, what's the rest of your schematic?

3

wvmarle:
Is the sensor in fact connected to A1?

If so, what's the rest of your schematic?

Yes, A1 to sensor pin1, GND to pin2 and 5v to pin3.

4

Okay, now I found solution. After I connect sensor directly to Arduino, it gives right values. With breadboard it fails.

5

Right... Values looked like a floating pin, i.e. not connected to anything.
Breadboards are prone to poor connections. Note also that on many breadboards the power rails are not connected all the way from one end to the other, that's another common pitfall. No power to the sensor often has the same effect.